JP2016509777A - Ultrasonic transducer electrode assembly - Google Patents

Abstract

The present invention provides a method for manufacturing an ultrasonic transducer. A substrate having a first side and a second side opposite the first side is provided. A lower electrode is formed on the first side of the substrate. A piezoelectric element is formed on the lower electrode. The piezoelectric element has a chamfered side wall. An upper electrode is formed over the piezoelectric element. A step metal member is formed over a portion of the upper electrode closest to the chamfered side wall of the piezoelectric element.

Description

TECHNICAL FIELD The present invention relates generally to intravascular ultrasound (IVUS) imaging, and more particularly to an electrode assembly for an ultrasound transducer.

Background Intravascular ultrasound (IVUS) imaging is used to evaluate blood vessels such as arteries in the human body to determine treatment needs, guide interventions, and / or assess their effectiveness. Widely used in cardiac intervention as a diagnostic tool. The IVUS imaging system uses ultrasound echoes to generate a cross-sectional image of the blood vessel of interest. Typically, IVUS imaging uses a transducer on an IVUS catheter that emits ultrasound signals (electromagnetic waves) and receives reflected ultrasound signals. Radiated ultrasound signals (often referred to as ultrasound pulses) easily pass through most tissues and blood, but do not allow tissue structures (such as various layers of the vessel wall), red blood cells, and other interests of interest. It is partially reflected by impedance changes caused by features. An IVUS imaging system connected to an IVUS catheter by a patient interface module (PIM) processes a received ultrasound signal (often referred to as ultrasound echo) to cross-section the vessel in which the IVUS catheter is located. Generate an image.

  IVUS catheters typically use one or more transducers to transmit ultrasound signals and receive reflected ultrasound signals. These transducers have electrodes that are used to apply electrical signals to the transducers. However, existing techniques for forming electrodes for transducers may have certain drawbacks. For example, conventional transducer electrodes may suffer from discontinuity problems.

  Thus, conventional methods of forming transducer electrodes have generally been adequate for their intended purpose, but have not been completely satisfactory in all respects.

Overview Ultrasonic transducers are used in intravascular ultrasound (IVUS) imaging to help assess internal medical conditions. As part of its operation, an ultrasonic transducer has electrodes that are used to apply electrical signals to the transducer. However, conventional ultrasonic transducers suffer from drawbacks such as electrode discontinuities, which can interfere with the intended electrical operation of the transducer. The present invention relates to an ultrasonic transducer that utilizes a step metal member to overcome the electrode discontinuity problem associated with conventional ultrasonic transducers. More specifically, the ultrasonic transducer has a piezoelectric film sandwiched between an upper electrode and a lower electrode. The upper electrode is disposed on the upper surface and the side wall of the piezoelectric film. The portion of the upper electrode located on the side wall of the piezoelectric film tends to suffer from discontinuity problems. Therefore, a step metal member (having the same material composition as the upper electrode itself) is formed on the side wall portion of the upper electrode. The step metal member functions as a bridge when an electrical discontinuity occurs on the side wall of the upper electrode.

  The present invention provides various embodiments of ultrasonic transducers for use in intravascular ultrasound (IVUS) imaging. A typical ultrasonic transducer includes a substrate, a lower electrode disposed on the substrate, a piezoelectric element disposed on the lower electrode, and an upper electrode disposed at least on an upper surface and a sidewall of the piezoelectric element; A step metal member disposed on a side wall of the upper electrode.

  The present invention further provides an ultrasound system. The ultrasound system includes an imaging component that includes a flexible elongate member and a piezoelectric micromachined ultrasonic transducer (PMUT) coupled to the distal end of the elongate member. The PMUT has a substrate having a front surface and a back surface opposite to the first surface, and is disposed on the substrate and extends from the back surface of the substrate to the front surface of the substrate, but beyond A non-well, at least partially filled with a backing material, and a transducer film disposed in the well comprising a piezoelectric element disposed between the upper and lower electrodes; A step metal member disposed on a side wall of the piezoelectric element. The ultrasound system also includes an interface module configured to engage the proximal end of the elongate member and an ultrasound processing component in communication with the interface module.

  The present invention further provides a method of forming an ultrasonic transducer. The method comprises providing a substrate having a first side and a second side opposite the first side; forming a lower electrode on the first side of the substrate; and forming a chamfered sidewall on the lower electrode. Forming an upper electrode on the piezoelectric element; and forming a step metal member on a portion of the upper electrode closest to the chamfered sidewall of the piezoelectric element.

  Both the foregoing general description and the following detailed description are exemplary and explanatory in nature and are intended to provide an understanding of the invention without limiting the scope of the invention. In this regard, additional aspects, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description.

  Aspects of the invention are best understood from the following detailed description when read with the accompanying figures. It is emphasized that the various features are not drawn to scale, according to standard practice in the art. In practice, the dimensions of the various features can be arbitrarily expanded or reduced for clarity of discussion. Furthermore, the present invention can repeat reference numerals and / or letters in various examples. This repetition is for purposes of simplicity and clarity and as such is not intended to prescribe the relationship between the various embodiments and / or configurations discussed.

FIG. 1 is a schematic diagram of an intravascular ultrasound (IVUS) imaging system according to various aspects of the present invention. FIG. 2 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 3 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 4 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture in accordance with various aspects of the present invention. FIG. 5 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture in accordance with various aspects of the present invention. FIG. 6 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture in accordance with various aspects of the present invention. FIG. 7 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 8 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 9 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 10 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture in accordance with various aspects of the present invention. FIG. 11 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 12 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture in accordance with various aspects of the present invention. FIG. 13 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture according to various aspects of the present invention. FIG. 14 is a schematic cross-sectional side view of an ultrasonic transducer at different stages of manufacture in accordance with various aspects of the present invention. FIG. 15 is a schematic top view of a portion of a transducer in accordance with various aspects of the present invention. FIG. 16A is a schematic top view of a via according to various aspects of the present invention. 16B-C are schematic top views of vias according to various aspects of the present invention. 16D-E are schematic top views of vias according to various aspects of the present invention. FIG. 17 is a flowchart of a method of manufacturing a transducer according to various aspects of the present invention.

DETAILED DESCRIPTION For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is intended. Any changes and further modifications in the described apparatus, systems and methods, as well as further applications of the principles of the present invention are fully contemplated and within the scope of the present invention. This is because those skilled in the art to which this disclosure is related will normally be devised. For example, although the present invention provides ultrasound imaging as described with respect to cardiovascular imaging, it should be understood that such description is not intended to be limited to this application. In some embodiments, the ultrasound imaging system includes an intravascular imaging system. This imaging system is also suitable for any application that requires imaging within a small cavity as well. In particular, it is fully contemplated that the features, components and / or processes described with respect to one embodiment can be combined with the features, components and / or processes described with respect to other embodiments of the invention. However, for simplicity, the multiple iterations of these combinations are not described separately.

  Currently, two types of catheters are commonly used: solid-state and rotary. A typical solid state catheter uses an array of transducers (usually 64) distributed around the catheter and connected to an electronic multiplexer circuit. The multiplexer circuit transmits an ultrasonic signal and selects a transducer from the array for receiving the reflected ultrasonic signal. By stepping through a series of transmit / receive transducer pairs, the solid state catheter can synthesize the effects of mechanically scanned transducer elements (but without moving parts). Because there are no rotating mechanical parts, the transducer array can be placed in direct contact with blood and vascular tissue with minimal risk of vascular trauma, and the solid state scanner can be configured with simple electrical cables and standard removable electrical connectors. Can be wired directly to the imaging system.

  A typical rotating catheter comprises a single transducer located at the distal end of a flexible drive shaft that rotates within a sheath that is inserted into a target vessel. The transducer is typically oriented so that the ultrasound signal propagates substantially perpendicular to the axis of the catheter. In a typical rotating catheter, a fluid-filled (eg, saline-filled) sheath protects vascular tissue from the rotating transducer and drive shaft, and frees ultrasonic signals from the transducer to the tissue. Allows propagation and return. As the drive shaft rotates (eg, at 30 revolutions per second), the transducer is periodically excited with high voltage pulses to emit short ultrasonic bursts. The ultrasonic signal is emitted from the transducer through a fluid-filled sheath and the sheath wall in a direction substantially perpendicular to the rotational axis of the drive shaft. The same transducer then waits for the return ultrasound signal reflected from the various tissue structures, and the imaging system is used for blood vessels from hundreds of these ultrasound pulse / echo acquisition sequences that occur during a single rotation of the transducer. Assemble a two-dimensional image of the cross section.

  FIG. 1 is a schematic diagram of an ultrasound imaging system 100 in accordance with various aspects of the present invention. In some embodiments, the ultrasound imaging system 100 includes an intravascular ultrasound imaging system (IVUS). The IVUS imaging system 100 includes an IVUS catheter 102 connected to an IVUS control system 106 by a patient interface module (PIM) 104. The control system 106 is connected to a monitor 108 that displays IVUS images (such as images generated by the IVUS system 100).

  In some embodiments, the IVUS catheter 102 is a rotating IVUS catheter, which is a Revolution® rotating IVUS imaging catheter available from Volcano Corporation and / or US Pat. No. 5,243,998 and US Pat. No. 5,546,948. It may be similar to the disclosed rotating IVUS catheter. Both of these documents are hereby incorporated by reference in their entirety. The catheter 102 includes an elongate flexible catheter sheath 110 (having a proximal end 114 and a distal end 116) shaped and configured for insertion into the lumen of a blood vessel (not shown). The longitudinal axis LA of the catheter 102 extends between the proximal end 114 and the distal end 116. The catheter 102 is flexible so that it can accommodate the curvature of the blood vessel during use. In this regard, the curved configuration shown in FIG. 1 is for illustrative purposes and is in no way limited to the manner in which the catheter 102 can be curved in other embodiments. In general, the catheter 102 can be configured to have any desired straight or arcuate profile in use.

  A rotating imaging core 112 extends within the sheath 110. The imaging core 112 has a proximal end 118 disposed within the proximal end 114 of the sheath 110 and a distal end 120 disposed within the distal end 116 of the sheath 110. The distal end 116 of the sheath 110 and the distal end 120 of the imaging core 112 are inserted into the target vessel during operation of the IVUS imaging system 100. The usable length of the catheter 102 (eg, the portion that can be inserted into the patient, particularly the target vessel) can be any suitable length and can vary depending on the application. The proximal end 114 of the sheath 110 and the proximal end 118 of the imaging core 112 are connected to the interface module 104. The proximal ends 114, 118 are attached to a catheter hub 124 that is removably connected to the interface module 104. The catheter hub 124 facilitates and supports a rotational interface that provides an electrical and mechanical connection between the catheter 102 and the interface module 104.

  The distal end 120 of the imaging core 112 includes a transducer assembly 122. The transducer assembly 122 is configured to rotate (by using a motor or other rotating device or method) to acquire an image of the blood vessel. The transducer assembly 122 can be of any suitable type for visualizing blood vessels, particularly stenosis within blood vessels. In the illustrated embodiment, the transducer assembly 122 comprises associated circuitry such as a piezoelectric micromachined ultrasonic transducer (“PMUT”) and an application specific integrated circuit (ASIC). A typical PMUT used for IVUS catheters can include a polymeric piezoelectric film as disclosed in US Pat. No. 6,641,540, which is incorporated herein by reference in its entirety. The PMUT transducer can provide over 75% bandwidth for optimal radial resolution and a spherical focal aperture for optimal azimuth and elevation resolution.

  The transducer assembly 122 can also include a housing having a PMUT transducer and associated circuitry disposed therein, wherein the housing is an opening through which an ultrasonic signal generated by the PMUT transducer travels. Have Alternatively, the transducer assembly 122 includes a capacitive micromachined ultrasonic transducer (“CMUT”). In yet another embodiment, the transducer assembly 122 comprises an ultrasonic transducer array (eg, some embodiments use an array having 16, 32, 64, or 128 members).

  The rotation of the imaging core 112 within the sheath 110 is controlled by the interface module 104, which provides user interface controls that can be manipulated by the user. The interface module 104 can receive, analyze and / or display information received via the imaging core 112. It will be appreciated that any suitable function, control, information processing and analysis and display can be implemented in the interface module 104. In one example, the interface module 104 receives data corresponding to ultrasound signals (echoes) detected by the imaging core 112 and forwards the received echo data to the control system 106. In one example, the interface module 104 performs preliminary processing of echo data before sending the echo data to the control system 106. The interface module 104 may perform echo data amplification, filtering and / or aggregation. The interface module 104 can provide high and low voltage DC power to support the operation of the catheter 102 including circuitry within the transducer assembly 122.

  In some embodiments, the wiring associated with the IVUS imaging system 100 can communicate signals from the control system 106 to the interface module 104 and / or communicate signals from the interface module to the control system. , Extending from the control system 106 to the interface module 104. In some embodiments, the control system 106 communicates with the interface module 104 wirelessly. Similarly, in some embodiments, wiring associated with the IVUS imaging system 100 can control signals from the control system 106 to and / or from the monitor to the control system. It can be seen that it extends from the system 106 to the monitor 108. In some embodiments, the control system 106 communicates with the monitor 108 wirelessly.

  2-14 are schematic partial cross-sectional side views of an exemplary ultrasonic transducer 200 for illustrating an electrode assembly for the transducer 200. 2-14 correspond to different stages of manufacture according to various aspects of the invention. 2 to 14 are simplified for the sake of clarity in order to better understand the technical idea of the present invention.

  Each ultrasonic transducer 200 may be included in the IVUS imaging system 100 of FIG. The ultrasonic transducer 200 is suitable for intravascular imaging because of its small size and high resolution. In some embodiments, the ultrasonic transducer 200 has a size on the order of tens or hundreds of microns, can operate in a frequency range of about 1 megahertz (MHz) to about 135 MHz, and is sub-50 micron. Resolution can be provided and transmission at a depth of at least 10 millimeters (mm) can be provided. In addition, the ultrasonic transducer 200 defines a target focus area based on the deflection depth of the transducer aperture, thereby generating an image useful for defining the vessel morphology beyond the surface characteristics. Is shaped to allow Various aspects of the ultrasonic transducer 200 and its manufacture are discussed in more detail below.

  In the illustrated embodiment, the ultrasonic transducer 200 is a piezoelectric micromachined ultrasonic transducer (PMUT). In other embodiments, the transducer 200 can include other types of transducers. Additional features can be added to the ultrasonic transducer 200, and some of the features described below can be used or eliminated in place of additional embodiments of the ultrasonic transducer 200.

  As shown in FIG. 2, the transducer 200 includes a substrate 210. The substrate 210 has a surface 212 and a surface 214 opposite to the surface 212. The surface 212 can also be referred to as the front or front side, and the surface 214 can be referred to as the back side or the back side. In the illustrated embodiment, the substrate 210 is a silicon microelectromechanical system (MEMS) substrate. The substrate 210 includes other suitable materials in other embodiments, depending on the design requirements of the PMUT transducer 200. In the illustrated embodiment, the substrate 210 is a “lightly doped silicon substrate”. In other words, the substrate 210 consists of a silicon wafer with a slight addition of dopant, resulting in a resistivity in the range of about 1 Ω / cm to about 1000 Ω / cm. One advantage of the “lightly doped silicon substrate” 210 is that it is relatively inexpensive compared to, for example, pure silicon or an undoped silicon substrate. Of course, it is understood that in other embodiments where cost is not as critical, pure silicon or undoped silicon substrates may be used.

  The substrate 210 can have various layers that are not shown separately and can be combined to form an electronic circuit that can comprise various microelectronic elements. These microelectronic elements include: transistors (eg, metal oxide semiconductor field effect transistors (MOSFETs), complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJT), high voltages. Transistors, high frequency transistors, p-channel and / or n-channel field effect transistors (PFET / NFET)); resistors; diodes; capacitors; inductors; fuses; and / or other suitable components. The various layers include high-k dielectric layers, gate layers, hard mask layers, interface layers, cap layers, diffusion / barrier layers, dielectric layers, conductive layers, other suitable layers, or combinations thereof. Logic elements, memory elements (eg, static random access memory (SRAM)), radio frequency (RF) devices, input / output (I / O) devices, system-on-chip (SoC) devices, other suitable type devices, or A plurality of microelectronic elements, such as a combination, can be interconnected to form part of an integrated circuit.

  An initial thickness 220 of the substrate 210 is measured between the surface 212 and the surface 214. In some embodiments, the initial thickness 220 ranges from about 200 microns (μm) to about 1000 μm.

  A dielectric layer 230 is formed on the surfaces 212 and 214 of the substrate 210. Dielectric layer 230 is used in the art such as thermal oxidation, low temperature oxide deposition, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or combinations thereof. It can be formed by any known suitable deposition process. The dielectric layer 230 can contain an oxide material or a nitride material such as silicon oxide, phosphorus silicate glass (PSG), silicon nitride, silicon oxynitride, or combinations thereof. Dielectric layer 230 provides a support surface for the layers formed thereon. The dielectric layer 230 provides electrical insulation. More specifically, in the illustrated embodiment, substrate 210 is a “lightly doped silicon substrate” that is relatively conductive, as described above. This relatively high conductivity of the substrate 210 can be problematic when the transducer 200 is pulsed with a relatively high voltage, for example, an excitation voltage of about 60 volts to about 200 volts DC. This means that it is undesirable for the bottom electrode of the transducer 200 (described in more detail below) to be in direct contact with the silicon substrate 210. In accordance with various aspects of the present invention, the dielectric layer 230 serves to insulate the bottom electrode of the transducer 230 from the relatively conductive surface of the silicon substrate 210.

  Next, a conductive layer 240 (ie, a lower electrode) is formed on the dielectric layer 230. The conductive layer 240 can be formed by a suitable deposition process such as sputtering, evaporation, CVD, PVD, ALD, or the like. In the illustrated embodiment, the conductive layer 240 includes a metal or a plurality of metallic materials. For example, the metal or metal materials include titanium, chromium, gold, aluminum, platinum, or combinations thereof.

  Referring to FIG. 3, the conductive layer 240 is patterned using techniques in a lift-off or photolithography process. Unnecessary portions of the conductive layer 240 are removed as part of the process. In some embodiments, the conductive layer can be deposited using a shadow mask to create a pattern.

  Next, the piezoelectric film 250 is formed on the dielectric layer 230 and the conductive layer 240. In various embodiments, the piezoelectric film 250 is made of polyvinylidene fluoride (PVDF) or a copolymer thereof, polyvinylidene fluoride / trifluoroethylene (PVDF / TrFE), polyvinylidene fluoride / tetrafluoroethylene (PVDF / TFE), or the like. The piezoelectric material can be included. Alternatively, polymers such as PVDF · CTFE and PVDF · CFE or sol-gel-forming piezoelectric materials can be used. In the illustrated embodiment, the piezoelectric material used for the piezoelectric film 250 contains PVDF · TrFE.

  The piezoelectric film 250 is patterned to achieve a desired shape, for example, the shape shown in FIG. Unnecessary portions of the piezoelectric film 250 are removed by a patterning process. As a result, portions of the dielectric layer 230 and the conductive layer 240 are exposed. For simplicity, FIG. 3 shows only the piezoelectric film 250 after it has been patterned.

  In this embodiment, the piezoelectric film 250 is etched in such a way as to form a chamfer so as to allow deposition to form the upper electrode. The chamfer can be shown as a trapezoidal side wall as shown in the cross-sectional view of FIG. The chamfer allows the conductive layer 270 to be deposited on the piezoelectric film 250 that is unlikely to be discontinuous. Also, in some embodiments, an adhesion promoting layer (not shown herein) is formed between the piezoelectric film 250 and the conductive layer 240 so that the piezoelectric film 250 is more easily adhered to the conductive layer 240. It is understood that you can. One embodiment of an adhesion promoting layer is disclosed in US Provisional Application No. 61/74512 (Dylan Van Hoven, Dylan Van Hoven, filed Dec. 21, 2012, entitled “Methods and Apparatus for Focusing Miniature Ultratransducers”). No. 44755.106).

  Referring now to FIG. 4, the conductive layer 270 (ie, the top electrode) is formed on the piezoelectric film 250 using a suitable deposition process known in the art. In the illustrated embodiment, the conductive layer 270 includes a metal or metal materials such as titanium, chromium, gold, aluminum, platinum, or combinations thereof. After its deposition, the conductive layer 270 is patterned using techniques in a photolithography process. Unnecessary portions of the conductive layer 270 are removed as part of the photolithography process. For simplicity, FIG. 4 only shows the conductive layer 270 after it has been patterned.

  The conductive layers 240 and 270 and the piezoelectric layer 250 (and the adhesion promoting layer (embodiment in which it is used)) can be collectively considered as a transducer film. It will be appreciated that pad metals may be formed to establish electrical connections to the conductive layers 240 and / or 270, but these pad metals are not shown here for purposes of simplicity.

  A potential problem associated with the deposition of conductive layer 270 (ie, the top electrode) is that there may be discontinuities in the deposited conductive layer 270. For example, referring to FIG. 5, an exemplary discontinuity 275 in the conductive layer 270 is shown. As described above, the piezoelectric film 250 is formed to have a chamfered part in order to avoid such discontinuity 275. Nevertheless, limitations and other deficiencies in the metal deposition process may still result in one or more discontinuities 275. The discontinuity 275 can cause an electrical open condition. In other words, the conductive layer 270 cannot be electrically connected to a target external device due to the discontinuity 275. This may prevent full electrical access to the transducer 200.

  According to various aspects of the present invention, the problem caused by the discontinuity 275 can be solved using a step metal member. The step metal can be formed by a suitable deposition process such as sputtering, evaporation, CVD, PVD, ALD, followed by a lift-off or photolithography pattern process. The formation of the step metal will be described below with reference to FIGS.

  Referring to FIG. 6, a photoresist material 280 is coated over the transducer 200 including the conductive layer 270.

  Referring to FIG. 7, openings 285 are formed in the photoresist material 280. The opening 285 is configured to have a width sufficient to expose a part of the side wall of the conductive layer 270 (that is, a part of the upper electrode formed on the side wall of the piezoelectric film 250). If there is a discontinuity 275, the opening 285 exposes the discontinuity 275 as well.

  Referring to FIG. 8, a step metal member 290 is formed in the opening 285. Step metal member 290 has a material composition substantially similar to that of conductive layer 270. In other words, in the illustrated embodiment, the step metal member 290 includes one or more metals such as titanium, chromium, gold, aluminum, or combinations thereof. Step metal member 290 is formed to have a vertical dimension 295 and a lateral or horizontal dimension 296. In some embodiments, the vertical dimension 295 ranges from about 0.5 μm to about 2 μm and the lateral dimension 296 ranges from about 30 μm to about 100 μm.

  Referring to FIG. 9, the photoresist material 280 is removed, for example, by a photoresist strip process. The step metal member 290 covers the side wall of the conductive layer 270 (upper electrode). It can be seen that if any discontinuity is present in the conductive layer 270, such as discontinuity 275, the step metal 290 will "shield" the discontinuity. In other words, the step metal 290 actually functions as a bridge for segments of the conductive layer 270 separated by discontinuities. As a result, electrical continuity is maintained throughout the conductive layer 270 by the step metal 290.

  It can be seen that the step metal member 290 is formed on the sidewall of the conductive layer 270. This is because the sidewalls of the conductive layer 270 are recognized as segments of the conductive layer 270 where discontinuities can occur. However, in another embodiment, the step metal member 290 (or other similar member) can be configured to form over other regions of the conductive layer 270 (these regions can also include discontinuities). ).

  In addition to (or instead of) the step metal member 290, the present invention forms metal vias to address the above discontinuity problem, as will be described in more detail below with reference to FIGS. can do. For reasons of consistency and clarity, identical or similar components found in FIGS. 2-9 and 10-14 are labeled the same.

  Referring to FIG. 10, a dielectric layer 230 (described above with respect to FIG. 2) is formed on the substrate 210. A conductive layer 240 (described above with respect to FIG. 2) is then formed on the dielectric layer 230.

  Referring to FIG. 11, conductive layer 240 is patterned into separate segments: segment 240 and segment 245. The segment 240 functions as a lower electrode of the transducer 200 and is hereinafter referred to as a lower electrode 240A. The segment 245 functions as the bottom of the upper electrode of the transducer 200 and is hereinafter referred to as the upper electrode segment 245. Next, the piezoelectric film 250 is formed over part of the lower electrode 240 </ b> A and part of the upper electrode segment 245. As described above, the piezoelectric film 250 can contain PVDF material or other suitable polymeric material.

  Referring to FIG. 12, the piezoelectric film 250 is patterned into segments 245 by vias. This via separates the piezoelectric film into two separate components 250A and 250B in this cross-sectional view. In some embodiments, component 250A is formed on upper electrode segment 245 and component 250B is formed on lower electrode 240A. However, in different embodiments this is not necessarily the case. As described above, in order to alleviate the problem of electrode discontinuities, both components 250A and 250B are formed with chamfers.

  Referring to FIG. 13, a conductive layer 270 is formed over the piezoelectric components 250A and 250B. The conductive layer 270 contains a metal or a plurality of metals such as titanium, chromium, gold, aluminum, platinum, or a combination thereof. The conductive layer 270 functions as the top of the upper electrode of the transducer 200 and is hereinafter referred to as the upper electrode segment 270.

  As shown in FIG. 13, a portion 270 </ b> A of the upper electrode segment 270 is formed on the upper electrode segment 245. This portion 270A can be referred to as a via 270A. In practice, via 270A increases the contact surface between upper electrode segment 270 (ie, the top of the upper electrode) and upper electrode segment 245 (ie, the bottom of the upper electrode). As a result, discontinuities are less likely to appear in the upper electrode.

  Additional processing steps may be performed to complete the manufacture of transducer 200. For example, an opening or well can be etched from the back side 214 to the substrate 210. The openings or wells can be filled with a backing material such as epoxy. Further, as shown in FIG. 14, the transducer film can be deformed into an arc shape (for example, by applying air pressure). These additional processing steps are described in US Provisional Application No. 61/74552 (Dylan Van Hoven 75, Dylan Van Hoven75, filed on Dec. 21, 2012, entitled "Methods and Apparatus for Focusing Miniature Transducers"). 1061).

  FIG. 15 is a simplified schematic plan view of a portion of the transducer 200 illustrating the embodiment of the step metal member 290 described above with reference to FIGS. For the sake of consistency and clarity, similar components will show the same in FIGS. As described above, the piezoelectric film 250 is formed so as to have a chamfered portion denoted by reference numeral 300, and enables good electrode continuity. The segment of the upper electrode 270 spans the chamfer 300. A step metal member 290 is formed on the chamfered portion 300 to ensure electrical continuity of the upper electrode 270.

  FIG. 16A is a simplified schematic plan view of a portion of transducer 200 illustrating the embodiment of via 270A described above with reference to FIG. For reasons of consistency and clarity, similar components show the same in FIGS. 13 and 16A. The cross-sectional view of FIG. 13 is obtained by taking a cross-section from point A to A ′ in the top view of FIG. 16A. As shown, via 270A effectively increases the contact surface area between the top segment of top electrode 270 and the bottom segment of the top electrode (not visible in FIG. 16A), thereby reducing the risk of discontinuity. .

  It will also be appreciated that in some embodiments, step metal members 290 and vias 270A can be implemented in transducer 200 to further improve electrode continuity.

  16B-16E show schematic top views of another embodiment of the via. For example, the embodiment shown in FIG. 16B shows a via serpentine large patch. The embodiment shown in FIG. 16C shows a via serpentine miniature patch. The embodiment shown in FIG. 16D shows a via fat large patch. The embodiment shown in FIG. 16E shows a via fat minipatch. However, regardless of the embodiment, it is understood that the larger one increases the contact surface area for the upper electrode and reduces the problem of electrode discontinuity.

  FIG. 17 is a flowchart of an ultrasonic transducer manufacturing method 500 in accordance with various aspects of the present invention. The method includes a step 510 of preparing a substrate. The substrate has a first side and a second side opposite to the first side. In some embodiments, the substrate contains silicon.

  Method 500 includes forming 520 a dielectric layer on the first side of the substrate. In some embodiments, the dielectric layer can include silicon oxide, silicon nitride, or silicon oxynitride.

  Method 500 includes a step 530 of forming a lower electrode over the entire surface of the substrate. The lower electrode can contain a metal or a plurality of metal materials such as titanium, chromium, gold, aluminum or combinations thereof. The lower electrode can be patterned.

  Method 500 includes forming 540 a piezoelectric element across the bottom electrode. The piezoelectric element has a chamfered side wall. In some embodiments, the piezoelectric element comprises polyvinylidene fluoride (PVDF), polyvinylidene fluoride / trifluoroethylene (PVDF / TrFE), polyvinylidene fluoride / tetrafluoroethylene (PVDF / TFE), or a sol-gel-forming piezoelectric material. Containing.

  Method 500 includes forming 550 an upper electrode across the piezoelectric element. The top electrode can contain a metal or a plurality of metallic materials such as titanium, chromium, gold, aluminum or combinations thereof. In some embodiments, the top electrode is disposed over the substrate, a top segment disposed on the top surface of the piezoelectric element, the top segment being a non-planar bottom segment, and coupling the top segment to the bottom segment And vias to be formed. Vias can be placed directly on the bottom segment. The via can include a recess in the upper electrode.

  The method 500 includes a step 560 of forming a step metal member over a portion of the upper electrode on the chamfered sidewall of the piezoelectric element. The step metal member and the upper electrode have substantially the same material composition.

  The method 500 includes forming 570 a well in the substrate from the second side. The well can be formed by an etching process. In some embodiments, the well is formed such that etching stops at the dielectric layer. In other embodiments, the well is formed such that the dielectric layer is also etched and etching stops at the lower surface of the substrate.

  The method 500 includes a step 580 of filling the well with a backing material. In some embodiments, the backing material comprises an epoxy material.

  Method 500 includes deforming 590 an upper electrode, a piezoelectric element, and a lower electrode (collectively constituting a transducer film) such that a portion of the transducer film disposed across the well has an arc shape.

  It should be understood that some of the above steps can be performed in a different order. It should also be understood that additional manufacturing steps can be performed to complete the manufacture of the transducer. However, these additional manufacturing steps are not described herein for reasons of simplicity.

  Those skilled in the art will appreciate that the apparatus, system and method can be varied in many ways. Accordingly, those skilled in the art will appreciate that the embodiments encompassed by the present invention are not limited to the specific exemplary embodiments described above. Although exemplary embodiments have been shown and described in this regard, a wide range of modifications, changes and substitutions are contemplated in the above disclosure. It is understood that such modifications can be made to the above items without departing from the scope of the present invention. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present invention.

100 Ultrasound Imaging System 102 IVUS Catheter 104 Patient Interface Module 106 IVUS Control System 108 Monitor 110 Sheath 122 Transducer Assembly 200 Transducer 210 Substrate 212 Surface 214 Surface 220 Initial Thickness 230 Dielectric Layer 240 Conductive Layer 250 Piezoelectric Film 270 Conductive Layer 270A Via 275 Discontinuous 280 Photoresist material 285 Opening 290 Step metal member 295 Vertical dimension 296 Lateral or horizontal dimension

Claims (29)

A micromachined ultrasonic transducer,
A substrate;
A lower electrode disposed on the substrate;
A piezoelectric element disposed on the lower electrode;
An upper electrode disposed at least on an upper surface and a side wall of the piezoelectric element;
A micromachined ultrasonic transducer comprising a step metal member disposed on a side wall of the upper electrode.   The micromachined ultrasonic transducer of claim 1, wherein the step metal member and the upper electrode have substantially similar material compositions.   The micromachined ultrasonic transducer according to claim 1, wherein the piezoelectric element has a chamfer.   The micromachined ultrasonic transducer of claim 1, further comprising a well disposed in the substrate.   The micromachined ultrasonic transducer of claim 4, wherein the well is at least partially filled with a backing material.   The micromachined ultrasonic transducer according to claim 4, wherein portions of the piezoelectric element disposed over the upper electrode, the lower electrode, and the well each have an arc shape.   The micromachined ultrasonic transducer of claim 1, further comprising a dielectric layer disposed between the substrate and at least the lower electrode.   The micromachined super-machine according to claim 1, wherein the piezoelectric element comprises polyvinylidene fluoride (PVDF), polyvinylidene fluoride / trifluoroethylene (PVDF / TrFE) or polyvinylidene fluoride / tetrafluoroethylene (PVDF / TFE). Sonic transducer. A top segment in which the upper electrode is disposed on an upper surface of the piezoelectric element;
Disposed over the substrate, the top segment being a non-planar bottom segment;
The micromachined ultrasonic transducer of claim 1, comprising a via that couples the top segment to the bottom segment.   The micromachined ultrasonic transducer of claim 9, wherein the via is disposed directly on the bottom segment.   The micromachined ultrasonic transducer of claim 9, wherein the via includes a recess in the upper electrode. Ultrasound system with:
An imaging component comprising a flexible elongate member and a piezoelectric micromachined ultrasonic transducer (PMUT) coupled to the distal end of the elongate member, wherein the PMUT is
A base material having a front surface and a back surface opposite to the first surface;
A well disposed on the substrate and extending from, but not exceeding, the back surface of the substrate, at least partially filled with a backing material;
A transducer film disposed in the well comprising a piezoelectric element disposed between an upper electrode and a lower electrode;
A step metal member disposed on a side wall of the piezoelectric element;
An interface module configured to engage a proximal end of the elongate member; and a sonication component in communication with the interface module.   The ultrasound system of claim 12, wherein the step metal member and the upper electrode have substantially similar material compositions.   The ultrasonic system according to claim 12, wherein the piezoelectric element has a chamfer.   The ultrasound system of claim 12, wherein the portion of the transducer membrane disposed across the well has an arc shape.   The ultrasound system according to claim 12, further comprising a dielectric layer disposed between the substrate and the lower electrode.   13. The piezoelectric element comprises polyvinylidene fluoride (PVDF), polyvinylidene fluoride / trifluoroethylene (PVDF / TrFE), polyvinylidene fluoride / tetrafluoroethylene (PVDF / TFE) or a sol-gel-forming piezoelectric material. An ultrasonic system as described in. A top segment in which the upper electrode is disposed on an upper surface of the piezoelectric element;
Disposed over the substrate, the top segment being a non-planar bottom segment;
Vias for coupling the top segment to the bottom segment;
The ultrasound system according to claim 12.   The ultrasound system of claim 18, wherein the via is disposed directly on the bottom segment.   The ultrasound system of claim 18, wherein the via includes a recess in the upper electrode. Next step:
Providing a substrate having a first side and a second side opposite the first side;
Forming a lower electrode on the first side of the substrate;
Forming a piezoelectric element having a chamfered sidewall on the lower electrode;
Forming an upper electrode on the piezoelectric element; and forming a step metal member on the portion of the upper electrode closest to the chamfered sidewall of the piezoelectric element. The upper electrode, the piezoelectric element and the lower electrode collectively form a transducer film and the following steps:
22. The method of claim 21, further comprising forming a well in the substrate from the second side; and deforming a portion of the transducer membrane disposed across the well into an arc shape.   23. The method of claim 22, further comprising filling the well with a backing material.   The method of claim 21, further comprising forming a dielectric layer over the first side of the substrate prior to forming the bottom electrode.   The method of claim 21, wherein the step metal member and the top electrode have substantially similar material compositions.   22. The piezoelectric element comprises polyvinylidene fluoride (PVDF), polyvinylidene fluoride / trifluoroethylene (PVDF / TrFE), polyvinylidene fluoride / tetrafluoroethylene (PVDF / TFE) or a sol-gel-forming piezoelectric material. The method described in 1. Forming the upper electrode, the top segment having the upper electrode disposed on the upper surface of the piezoelectric element;
Disposed over the substrate, the top segment being a non-planar bottom segment;
The method of claim 21, wherein the method is implemented with a via that couples the top segment to the bottom segment.   28. The method of claim 27, wherein the via is placed directly on the bottom segment.   28. The method of claim 27, wherein the via includes a recess in the upper electrode.